Communication systems based on communication buses, such as CAN buses and LIN buses, are frequently used as those which are installable in motor vehicles. For example, such communication systems are disclosed in “DETAILED DESCRIPTION OF VEHICLE NETWORK SYSTEM”, MICHIO SATO, published on Dec. 1, 2005, CQ PUBLISHING CO., LTD.
A communication system of this type is comprised of a plurality of nodes communicably connected to a communication bus; these nodes are, for example, hardware computing terminals or software modules. Each node in the communication system is equipped with a signal processor, such as a CPU and a sequencer, and a transceiver for transmitting and receiving, via the communication bus, an encoded digital signal; the encoded digital signal includes sampled data from a transmission data signal supplied from the signal processor and clock information.
In order to improve data transfer efficiency of such a communication system, it is desirable to synchronize the transceivers of the respective nodes in a communication system with each other.
One technical approach to implement such synchronization is known. The technical approach is designed such that the transceiver of a node samples data from a transmission data signal supplied from the signal processor, and encodes the sampled data such that an encoded digital signal includes the sampled data and clock information. Then, the transceiver transmits the encoded digital signal to a communication bus.
At that time, an alternative node recovers the clock information from the encoded digital signal on the bus communication. Then, the alternative node divides the frequency of a self-clock generated by itself to generate a bus clock, which is synchronized with a clock defined by the clock information, so that the transceiver operates on the bus clock.
Recently, in view of reduction in power consumption and in cost, the transceiver of each node of these communication systems can be equipped with a simple oscillator, such as a ring oscillator, for generating a self-clock with a frequency (clock frequency) being of moderate accuracy.